The present invention is directed to a method for data transmission between a control unit for restraint devices and sensors.
The effectiveness of restraint systems in vehicles may improve sharply in the future in order to further improve the protection for the vehicle occupants. This may mean that the number of restraint devices in the vehicle will increase.
These restraint devices may then include, for example, multi-stage ignitable airbags for the driver and front seat passenger, knee bags for the driver and front seat passenger, side airbags for the driver, front seat passenger and rear occupants, side airbags being provided for both the head as well as for the chest area. In addition, restraint devices include belt tensioners, which also have multi-stage activation, roll bars, etc. Thus a complex protection system made up of a plurality of restraint devices is installed in the vehicle for every occupant.
In order to activate all these restraint devices so that they offer the vehicle occupants effective protection, a large number of sensors may be required to detect accident-specific vehicle parameters. These include sensors which detect the vehicle acceleration in various directions at various locations of the vehicle, pre-crash sensors, angular rate sensors, sensors which monitor the vehicle interior to detect the type of seat occupancy, the position of the vehicle occupants, child seats, etc.
A control unit present in the vehicle, which controls the deployment of the individual restraint devices, is connected to all the sensors in order to analyze their signals. It is believed that the introduction of a bus system which interconnects all sensors and the control unit makes it possible to dispense with voluminous wiring harnesses. Such a bus system for a large number of sensors, as explained in the introduction, is discussed, for example in European Patent Application No. 0 407 391.
According to this reference, the control unit determines the number and types of the operational sensors available and assigns a consecutive number to each sensor detected before a data transmission occurs between it and the individual sensors. This consecutive number stipulates the sequence of the communication of the sensors with the control unit. During the communication of the control unit with the sensors, all sensors always transmit in the same chronological sequence according to their assigned number in permanently set time slots.
An object of the exemplary embodiment of the present invention is to provide a method for providing flexible access of the control unit to the measured data of the individual sensors over time.
In this regard, the control unit transmits a request message to the sensors and that each sensor, by comparing the request message with its own address, derives whether and in what time slot it should transmit its data to the control unit. In this way, it is believed that time slots can be flexibly assigned to the individual sensors for the transmission of their measured data to the control unit. In this way, the priorities of the individual sensors can be adapted to different vehicle types or accident scenarios.
It may thus be provided that the agreement of at least one part of their address made up of a plurality of bits with at least one part of the request message made up of a plurality of bits provides information for the sensors as to whether the sensor in question should transmit its data continuously in a fixed time pattern or whether it should transmit its data once in a time slot identified by the request message. Also, time slots may be assigned to a plurality of sensors with one request message, of which one part agrees with one part of the addresses of a plurality of sensors.
It is believed to be expedient to have the sensors, whose recorded measured values are to be processed by the control unit with as little time delay as possible, transmit their data in time slots which are located at the end of the time slot sequence.
Also, the control unit may transmit a plurality of control bits together with the request message via the bus line, the control bits reporting to the sensors addressed by the request message that either they should select a specific memory register from a plurality present within them so that information can be written to it and read out of it, or information should be written into the selected memory register, or information should be read out of the selected memory register, or measured data should be transmitted to the control unit.